What are the side effects of the Moderna vaccine?

side effects of the Moderna vaccine
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Here we list some of the most common and uncommon side effects of the Moderna vaccine and discuss the latest trials on pediatric participants

Recently the US pharmaceutical company, Moderna, announced that it will begin testing its COVID-19 vaccine on children aged 6 months to 11 years old. It is the first manufacturer in the US to test its vaccine on infants.

Currently, the vaccine should not be administered to those under the age of 18 due to the unknown side effects.

But what side effects can the rest of the population expect if they are immunised?

Common side effects

The vaccine will be given to you as two 0.5 mL injections and it is recommended that the second dose be administered 28 days after the first.

According to the Medicines and Healthcare products Regulatory Agency around 1 in 10 people can expect to experience very common side effects such as:

  • Tenderness and swelling of the injection site and underarm glands
  • Headache
  • Nausea
  • Vomiting
  • Muscle ache/joint aches/ stiffness
  • Fatigue (tiredness)
  • Chills/ Fever
  • Rash

As with most medicines, mild side effects like those listed above can occur and are not a cause for concern but if you are worried about any side effects you can report it directly to the Coronavirus Yellow Card reporting site. 

Uncommon side effects

Some of the more uncommon/rare or unknown side effects that may still occur include:

  • Temporary one-sided facial drooping (Bell’s palsy)
  • Swelling of the face (It should be noted that swelling of the face can occur in patients who have had facial cosmetic injections.)
  • Severe allergic reactions (anaphylaxis)
  • Hypersensitivity

How effects is the Moderna vaccine?

During clinical trials, the company announced that the vaccine proved to be 94.1% effective and has also shown to work on the South African variant. 

Moderna ingredients

The active substance in each dose is 0.10 mg mRNA encoding the pre-fusion stabilized Spike glycoprotein of SARS-CoV-2 embedded in lipid nanoparticles. It also contains polyethylene glycol/macrogol (PEG) as part of PEG2000-DMG and is a multidose vial which contains 10 doses of 0.5 mL.

Other ingredients listed include:

  • Lipid SM-102, cholesterol
  • 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)
  • 1,2-Dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 (PEG2000-DMG)
  • Trometamol (tris)
  • Trometamol hydrochloride (tris HCl)
  • Acetic acid
  • Sodium acetate trihydrate
  • Sucrose
  • Water for injections

If you know you are allergic to any of the ingredients listed above then you should not have this particular vaccine.

You should also consult your doctor first if you have a weakened immune system, have a bleeding problem or have a high fever or severe infection.

Moderna expects to deliver its first vaccines to the UK in April.

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  1. I’ve had a low grade fever starting 24 hours after receiving the first shot, 3 weeks since I tested positive with the virus. It’s day 4 of low grade fever. Normal?


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